This invention relates generally to development apparatus for mixing and applying developer material to a latent image on an image-bearing member in an electrostatographic reproduction machine, such as a copier or printer. More particularly, this invention relates to a blender of the type for mixing electrostatographic developer comprising a plurality of blender segments mounted on a shaft.
Development apparatus, for example a magnetic brush development apparatus, are well known for mixing and applying developer material to a latent electrostatic image on a photoconductor in an electrostatographic reproduction machine such as a copier or printer. Such a development apparatus typically includes an elongate housing which has a sump portion for containing the developer material. A two-component developer material comprises a mixture of carrier particles and toner particles. These particles are usually moved and mixed by a mixing device in the sump portion of the housing for triboelectrically charging the particles. Mixing also promotes uniformity in the concentration of toner particles throughout the sump portion, and in the distribution of developer material within the sump. The mixed and charged developer material can then be fed from the sump portion for development of the latent image on the photoconductor, which is generally a film or drum.
The quality of such an image development depends, in significant part, on factors such as the level of charge on the toner particles achieved triboelectrically for example, and such as the level and uniformity of the concentration of toner particles in the developer material being applied. As is well known, these factors are mainly determined by the effectiveness of a mixing device used in the sump portion of the development apparatus housing for moving, mixing and charging the developer material particles.
Certain prior blender assemblies implement a row of blender segments mounted on a shaft. Such assemblies typically exhibit a looseness in the blender segments after assembly due to tolerance stack-up. The segments are able to move small distance relative to the shaft and relative to each other. This movement, although limited, can cause toner flakes in the developer which, in turn, causes objectionable artifacts in the developed image. In addition, the outside diameter of certain blenders is ground during manufacturing to ensure an accurate fit with the developer housing. Looseness in the segments can cause the segments to chatter during the grinding operation.
According to an aspect of the invention, a blender for mixing electrostatographic developer is provided, comprising a shaft having a pair of stops spaced along a length thereof, a plurality of blender segments of the type for mixing electrostatographic developer, each blender segment having an aperture, the shaft being received within the aperture of each blender segment, and a resilient spacer, wherein the resilient spacer and the plurality of blender segments are compressed between the pair of stops.
According to a further aspect of the invention, a method of fabricating a blender for mixing electrostatographic developer is provided, comprising disposing a resilient spacer and a plurality of blender segments of the type for mixing electrostatographic developer on a shaft, each blender segment having an aperture, the shaft being received within the aperture of each blender segment, and compressing the resilient spacer and the plurality of blender between a pair of stops on the shaft.
According to a still further aspect of the invention a blender for mixing electrostatographic developer is provided, comprising a shaft having a pair of stops spaced along a length thereof and a plurality of serrations, one of the stops comprising a snap ring engaging one of the serrations, a plurality of blender segments of the type for mixing electrostatographic developer, each blender segment having an aperture, the shaft being received within the aperture of each blender segment, and at least one belleville washer disposed immediately adjacent one of the stops, wherein the resilient spacer and the plurality of blender segments are compressed between the pair of stops.
A blender according to the present invention has a plurality of blender segments exhibiting no residual looseness due to tolerance stack-up.